All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is not valid to perform the Friday prayer on board a ship – even though it does not sail – because it is not a place of permanent residence. One of the conditions of the validity of the Friday prayer is that it should be performed in a large city, town, village or a place that is annexed to it. Since the obligation of performing the Friday prayer is relieved from those living on board of a ship, they have to offer the Thuhr prayer instead.
Allaah Knows best.